Grasping device

ABSTRACT

A grasping device of the embodiment includes claw holding parts, a cam, pins, a motor, and a rail holding part. The claw holding parts are supported by rails in a slidable manner. The cam includes grooves or curved holes having a spiral shape provided around the rotation center and a hole provided at the rotation center. The pins each have one end engaged with the claw holding parts side and the other end engaged with the grooves or the curved holes of the cam. The motor includes a shaft to be fixed to the hole of the cam. The rail holding part is configured to hold the rails and engage a positioning jig with an end portion of the shaft at the side fixed to the cam and including a hole part with an inner peripheral surface where the outer peripheral surface of the jig is contactable.

TECHNICAL FIELD

The present invention relates to a grasping device.

BACKGROUND ART

In the related art, automation of production lines has been promoted toreduce production costs and stabilize quality, and automation usingrobots has been introduced to many production lines because of theversatility. A grasping device for grasping workpieces, such as parts,in such robots includes a grasping part including a plurality of clawparts and a driving part for driving the plurality of claw parts (see,for example, PTL 1, etc.).

A grasping device including a grasping part of a type with opposite twoclaw parts sliding to contact and separate from each other sometimesuses a cam provided with a groove or a curved hole having a spiral shapeto slide the claw parts. With such a configuration, the rotation of thecam causes the pin engaged with the groove or the curved hole of the camto move toward and away from the rotation axis, enabling the claw partsto slide.

CITATION LIST Patent Literature

-   JP 2016-144863A

SUMMARY OF INVENTION Technical Problem

In the above-described cam, however, the contact between the groove ofthe cam and the pin connected to the claw parts should be properly made,but it is difficult to perform accurate positioning during theassembling. When the positioning is not accurately performed, theefficiency of the slide movement may be decreased, or the cam may beworn.

In view of the above, an object of the present invention is to provide agrasping device capable of performing proper contact between the grooveof the cam and the pin through accurate positioning and preventingdecrease in efficiency of the slide movement and wear of the cam.

Solution to Problem

To solve the above-described problems and achieve the object, a graspingdevice according to an aspect includes claw holding parts, a cam, pins,a motor, and a rail holding part. The claw holding parts are supportedby rails in a slidable manner. The cam includes grooves or curved holeshaving a spiral shape provided around the rotation center and a holeprovided at the rotation center. The pins each have one end engaged withthe claw holding parts side and the other end engaged with the groovesor the curved holes of the cam. The motor includes a shaft to be fixedto the hole of the cam. The rail holding part configured to hold therails and engage a positioning jig with an end portion of the shaft atthe side fixed to the cam and including a hole part with an innerperipheral surface where the outer peripheral surface of the jig iscontactable.

The grasping device according to an aspect of the present invention canprovide a grasping device capable of performing proper contact betweenthe grooves of the cam and the pins through accurate positioning andpreventing decrease in efficiency of the slide movement and wear of thecam.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory diagram of a robot according to an embodiment.

FIG. 2 is a front view illustrating a configuration of a grasping deviceaccording to the embodiment.

FIG. 3 is a side view illustrating the configuration of the graspingdevice according to the embodiment.

FIG. 4 is a perspective view illustrating a configuration of a fixingpart according to the embodiment.

FIG. 5 is a diagram (1) for describing a driving mechanism of thegrasping device according to the embodiment.

FIG. 6 is an exploded view of a main part of a grasping part.

FIG. 7 is a diagram (2) for describing the driving mechanism of thegrasping device according to the embodiment.

FIG. 8 is a perspective view illustrating a configuration of a camaccording to the embodiment.

FIG. 9 is a flowchart illustrating a production step for the cam.

FIG. 10 is a flowchart illustrating an assembling step for the graspingdevice.

FIG. 11 is a perspective view illustrating a state in each assemblingstep for the grasping device.

FIG. 12 is a longitudinal sectional view illustrating when the cam isfixed to a shaft of a motor of a driving part.

FIG. 13 is a longitudinal sectional view illustrating when the graspingpart is fixed to the driving part and the fixing part.

FIG. 14 is a perspective view (1) of a rail holding part.

FIG. 15 is a perspective view (2) of the rail holding part.

DESCRIPTION OF EMBODIMENTS

A grasping device according to the embodiment is described withreference to the accompanying drawings. Note that the present inventionis not limited to the embodiment described above. Further, thedimensional relationships between elements, proportions of the elements,and the like in the drawings may differ from reality. Among thedrawings, parts having mutually different dimensional relationships andproportions may be included. Furthermore, the contents described in oneembodiment or modification example are applied in principle to otherembodiments or modification examples.

Overview of Robot

First, an overview of a robot 1 where a grasping device 10 according tothe embodiment is attached is described with reference to FIG. 1 . FIG.1 is an explanatory diagram of the robot 1 according to the embodiment.The robot 1 is an example of a moving mechanism for moving the graspingdevice 10 to a desired position. Note that the moving mechanism formoving the grasping device 10 to a desired position is not limited to arobot and may be, for example a linear actuator.

The robot 1 is a so-called articulated robot including a plurality ofjoint parts (also referred to as robot modules) 3 and is installed atproduct assembly lines or manufacture lines, for example. Note that forconvenience of description, FIG. 1 illustrates a three-dimensionalorthogonal coordinate system including a Z axis having a vertical upwarddirection as a positive direction. Such an orthogonal coordinate systemmay be illustrated in other drawings.

The robot 1 includes a base part 2, a plurality of joint parts 3, aplurality of arm parts 4, and the grasping device 10. Note that FIG. 1illustrates an example of the robot 1 including six joint parts 3 andtwo arm parts 4.

The six joint parts 3 are disposed in the order of a first joint part3A, a second joint part 3B, a third joint part 3C, a fourth joint part3D, a fifth joint part 3E, and a sixth joint part 3F between the basepart 2 at the upstream side of the power transfer in the robot 1 and thegrasping device 10 at the downstream side. In addition, of the two armparts 4, a first arm part 4A is disposed at the upstream side of thepower transfer in the robot 1 and a second arm part 4B is disposed atthe downstream side.

The base part 2 totally supports the robot 1 by supporting the firstjoint part 3A. The first joint part 3A of the six joint parts 3 rotatesaround an axis AX1 as a virtual axis with respect to the base part 2.The first joint part 3A rotates (also referred to as turns) in the X-Yplane. The second joint part 3B is coupled with the first joint part 3Aand rotates around an axis AX2 with respect to the first joint part 3A.

In addition, the second joint part 3B is coupled with one end portion ofthe first arm part 4A. The third joint part 3C is coupled with the otherend portion of the first arm part 4A. The fourth joint part 3D iscoupled with the third joint part 3C and rotates around an axis AX3 as avirtual axis with respect to the third joint part 3C. In addition, thefourth joint part 3D is coupled with one end portion of the second armpart 4B and rotates around axis AX4 as a virtual axis with respect tothe second arm part 4B.

The fifth joint part 3E is coupled with the other end portion of thesecond arm part 4B. The sixth joint part 3F is coupled with the fifthjoint part 3E and rotates around an axis AX5 as a virtual axis withrespect to the fifth joint part 3E. The grasping device 10 is coupledwith the sixth joint part 3F. The grasping device 10 rotates around anaxis AX6.

The grasping device 10 is attached to the sixth joint part 3F located ata leading end portion of the robot 1 and grasps workpieces, such asparts. A configuration of the grasping device 10 will be describedlater.

Note that the rotation configuration of the robot 1 with the six jointparts 3 is not limited to the above-mentioned configuration. The robot 1may be rotatable between the second joint part 3B and the first arm part4A or between the fourth joint part 3D and the second arm part 4B, forexample.

In addition, the six joint parts 3 each include a rotation actuator notillustrated in the drawing. The robot 1 can perform multi-axis operationwith such a rotation actuator.

Configuration of Grasping Device

Next, a configuration of the grasping device 10 according to theembodiment is described with reference to FIG. 2 to FIG. 4 . FIG. 2 is afront view illustrating a configuration of the grasping device 10according to the embodiment, and FIG. 3 is a side view illustrating theconfiguration of the grasping device 10 according to the embodiment.FIG. 4 is a perspective view illustrating a configuration of a fixingpart 40 according to the embodiment.

As illustrated in FIG. 2 and FIG. 3 , the grasping device 10 includes agrasping part 20, a driving part 30, the fixing part 40, and an encoder50. The grasping part 20 grasps workpieces, such as parts. The graspingpart 20 includes claw parts 21 a and 21 b, claw holding parts 22 a and22 b, rails 23 a and 23 b, and a rail holding part 24.

The claw parts 21 a and 21 b are movable in respective predetermineddirection and grasp such a workpiece by sandwiching the workpiece. Notethat FIG. 2 and FIG. 3 illustrate the shapes of the claw parts 21 a and21 b with a leading end portion gradually tapered, but the shapes of theclaw parts 21 a and 21 b are not limited to such shapes and may beappropriately changed in accordance with the types of workpieces to begrasped.

The claw holding part 22 a holds the claw part 21 a, and the clawholding part 22 b holds the claw part 21 b. The claw holding parts 22 aand 22 b are movable in predetermined direction together with the clawparts 21 a and 21 b, respectively. The rails 23 a and 23 b extend inrespective predetermined directions. For example, the rail 23 a and therail 23 b extend in substantially parallel to each other.

The rail holding part 24 includes a base part 24 a having a flat plateshape, and a pair of wall parts 24 b extending from the base part 24 ato a substantially perpendicular direction. The rails 23 a and 23 b areheld by the pair of respective wall parts 24 b. Note that a specificconfiguration of the grasping part 20 will be described later.

The driving part 30 drives the claw parts 21 a and 21 b. The drivingpart 30 includes a motor 31 and a shaft 32 (see FIG. 5 ). The motor 31generates a driving force for driving the claw parts 21 a and 21 b. Theshaft 32 transmits the driving force generated at the motor 31 to thegrasping part 20.

Note that any type of the motor 31 is used in the embodiment, and hybridstepper motors, DC motors and the like may be used. In addition, detailsof the driving mechanism of the claw parts 21 a and 21 b by the drivingpart 30 will be described later.

The fixing part 40 fixes the grasping part 20 and the driving part 30described above to the sixth joint part 3F of the robot 1. Asillustrated in FIG. 4 , the fixing part 40 has a substantial U-shape,and includes a supporting part 41, a coupling part 42 and a beam part43. The fixing part 40 can be manufactured, for example, by bendingsheet metal or by machining a metal block.

The supporting part 41 has a substantially flat plate shape and supportsthe grasping part 20 and the driving part 30 between the grasping part20 and the driving part 30. For example, the supporting part 41 supportsthe rail holding part 24 of the grasping part 20 on one surface side (inFIG. 2 and FIG. 3 , the negative direction side in the Z axis), andsupports the driving part 30 on the other surface side (in FIG. 2 andFIG. 3 , the positive direction side in the Z axis). The supporting part41 is provided with an opening 44 where an annular protrusion part 38(FIG. 5 ) provided to surround the shaft 32 is fit at one end surface ofthe driving part 30 in the axis direction.

The coupling part 42 has a substantially flat plate shape and is coupledwith the sixth joint part 3F of the robot 1. For example, as illustratedin FIG. 4 , a screw hole 42 a is formed at a predetermined position ofthe coupling part 42, and the coupling part 42 can be coupled to thesixth joint part 3F through threaded engagement using the screw hole 42a with a screw, a bolt, or the like. The coupling part 42 is provided ata substantially parallel position facing the supporting part 41, forexample.

Note that a hole 42 b is provided at a substantial center of thecoupling part 42. The hole 42 b is a through hole where a pressing rod92 of a jig is inserted when a cam 27 is fixed (press-fitted) to theshaft 32 of the driving part 30 described later. The cam 27 is forcausing the claw parts 21 a and 21 b to slide. Note that a hole is alsoprovided at the bottom portion (bottom portion of a motor case 33) ofthe driving part 30 fixed to the coupling part 42 at a positioncorresponding to the hole 42 b, allowing the shaft of the jig to pressthe shaft 32 of the driving part 30 from the outside through thecoupling part 42 of the fixing part 40 and the bottom portion (thebottom portion of the motor case 33) of the driving part 30.

The beam part 43 has a substantially flat plate shape and connects thesupporting part 41 and the coupling part 42. The beam part 43 issubstantially perpendicular to the supporting part 41 and the couplingpart 42, for example.

As described above, in the grasping device 10 of the embodiment, thegrasping part 20 is fixed to the robot 1 through the fixing part 40.That is, in the embodiment, the grasping part 20 is fixed to the robot 1without the driving part 30 interposed.

The encoder 50 detects the rotation position of the motor 31. Theencoder 50 is provided at the motor 31 side from the supporting part 41of the fixing part 40. For example, the encoder 50 is provided at theside opposite to the supporting part 41 with respect to the motor 31.Note that any type of the encoder 50 is used in the embodiment, andoptical encoders, magnetic encoders and the like may be used. Thedistance or the speed of the claw parts 21 a and 21 b can be accuratelycontrolled based on the information of the encoder 50. Note that in thecase where it is unnecessary to accurately control the distance or thespeed of the claw parts 21 a and 21 b, the encoder 50 may be omitted.

Driving Mechanism of Grasping Device

Next, details of the driving mechanism of the grasping device 10 aredescribed with reference to FIG. 5 to FIG. 8 . FIG. 5 and FIG. 7 arediagrams for describing the driving mechanism of the grasping device 10according to the embodiment. FIG. 6 is an exploded view of a main partof the grasping part 20. FIG. 8 is a perspective view illustrating aconfiguration of the cam 27 according to the embodiment. Note that FIG.5 and FIG. 7 omit the illustration of the claw parts 21 a and 21 b, therail holding part 24, the fixing part 40 for easy understanding. FIG. 6omits the illustration of the parts other than the claw holding parts 22a and 22 b, the rails 23 a and 23 b, slide movement parts 25 a and 25 b,and pins 26 a and 26 b.

As illustrated in FIG. 5 to FIG. 7 , the slide movement part 25 a isslidable being guided by the rail 23 a, and the slide movement part 25 bis slidable being guided by the rail 23 b. That is, the slide movementpart 25 a slides along the extending direction of the rail 23 a, and theslide movement part 25 b slides along the extending direction of therail 23 b.

In addition, the claw holding part 22 a is fixed to the slide movementpart 25 a, and the claw holding part 22 b is fixed to the slide movementpart 25 b. In addition, as illustrated in FIG. 5 , the pin 26 a is fixedto the claw holding part 22 a, and the pin 26 b is fixed to the clawholding part 22 b. Note that bearings are provided at the leading endsof the pins 26 a and 26 b. Thus, the claw holding part 22 a and the pin26 a slide in unison with the slide movement part 25 a, and the clawholding part 22 b and the pin 26 b slide in unison with the slidemovement part 25 b.

The cam 27 transmits the driving force from the motor 31 to the pins 26a and 26 b. As illustrated in FIG. 8 , the cam 27 has a substantiallycircular plate shape and includes spiral grooves 27 a and 27 b and acircular hole 27 c. The grooves 27 a and 27 b are formed to spiralgradually away from (or approaching) the center of the cam 27. Thecircular hole 27 c is formed at the rotation center the cam 27 and is afitting part with the shaft 32 of the motor 31. Note that the grooves 27a and 27 b are a spiral recess part with a bottom provided at onesurface as an advantage to maintain the strength of the cam 27, but acurved hole in the form of a bottomless through hole may be provided ifaccepted in terms of strength.

Then, as illustrated in FIG. 5 , the pin 26 a is slidably inserted tothe groove 27 a of the cam 27, and the pin 26 b is slidably inserted tothe groove 27 b. In addition, the shaft 32 extending from the motor 31is inserted to the circular hole 27 c, and the cam 27 is fixed to theshaft 32.

The shaft 32 rotates with the driving force generated by the motor 31.Thus, the cam 27 rotates with the driving force of the motor 31 throughthe shaft 32.

Here, when the cam 27 is rotated in a predetermined rotational directionR1 with the motor 31, a force in the direction toward the center of thecam 27 is applied to the pins 26 a and 26 b guided by the spiral grooves27 a and 27 b.

Here, the pin 26 a is slidable along the rail 23 a in unison with theslide movement part 25 a. In this manner, the pin 26 a moves in apredetermined direction D1. The direction D1 is the direction toward thecenter of the cam 27 and the extending direction of the rail 23 a.

Further, the pin 26 a is fixed to the claw holding part 22 a, andtherefore the claw holding part 22 a and the claw part 21 a notillustrated in the drawing move in a direction D2 having the samedirection as the above-described direction D1.

Likewise, the pin 26 b is slidable along the rail 23 b in unison withthe slide movement part 25 b. In this manner, the pin 26 b moves in apredetermined direction D3. The direction D3 is the direction toward thecenter of the cam 27 and the extending direction of the rail 23 b.

Further, the pin 26 b is fixed to the claw holding part 22 b, andtherefore the claw holding part 22 b and the claw part 21 b notillustrated in the drawing move in a direction D4. The direction D4 isthe same direction as the above-described direction D3.

The rail 23 a and the rail 23 b are disposed substantially parallel witheach other, and thus the driving part 30 can move the claw parts 21 aand 21 b in the directions D2 and D4 as the directions close each otherby rotating the cam 27 in the rotational direction R1. Conversely, thedriving part 30 can move the claw parts 21 a and 21 b in the directionsaway from each other by rotating the cam 27 in the direction opposite tothe rotational direction R1.

With the mechanism described above, in the embodiment, workpieces can begrasped with the claw parts 21 a and 21 b by appropriately controllingthe distance of the claw parts 21 a and 21 b by rotating the motor 31.

In addition, in the embodiment, the motor 31 is provided between thesupporting part 41 and the encoder 50. In this manner, when a stress isapplied to the grasping part 20 from the workpiece, the stress isabsorbed by the fixing part 40 through the supporting part 41, and thusthe vibration of the encoder 50 due to such a stress can be suppressed.As a result, the detection accuracy of the encoder 50 can be improved.

Production of Cam

FIG. 9 is a flowchart illustrating a production step for the cam 27. InFIG. 9 , first, the cam 27 before sintering is produced through metalmolding using a sintered material for metal molding (step S11). An ironsintered material is used as the sintered material for metal molding,for example. With the iron sintered material, the cam 27 with a highstrength can be obtained. Since the external shape is shrank throughsintering at the next step, the metal mold for molding the cam 27 beforesintering is designed in consideration of the amount of the shrinkage.

Next, the cam 27 before sintering is subjected to sintering (step S12).The cam 27 is cured through the sintering. The cam 27 before sinteringis molded in a uniform size through the metal molding, and the amount ofthe shrinkage in the sintering is accurately managed. Thus, incomparison with the case of one-by-one production through machining suchas cutting and wire cutting, the production is performed in a low-costmanner, and the variation in dimensions can be small (ensuring thedimensional accuracy).

Next, the cam 27 after sintering is subjected to carburizing andquenching (step S13). In the carburizing and quenching, carbon is addedto the surface of the cam 27 through gas carburizing and the like,followed by hardening and tempering, and the carbon permeates thesurface. Through the carburizing and quenching, a carburizing layer isformed at the surface of the cam 27, and thus the hardness of thesurface can be increased. That is, the grooves 27 a and 27 b of the cam27 are portions where the bearings provided at the pins 26 a and 26 bslide, and the resistance to wearing can be increased when provided witha hardness equal to or greater than the hardness of the bearing.

Next, the cam 27 is subjected to resin impregnation (step S14). In theresin impregnation, for example, immersion in liquid of acrylicthermosetting resin as a sintering sealing material is performed, andsolidification is performed through heating or the like after the resinis impregnated. In the cam 27 after sintering, multiple micro porousportions (holes) are formed in the surface, and the porous portions ofthe surface are filled with the resin material through the resinimpregnation. In the state where the cam 27 is incorporated in thegrasping device 10, grease is applied for lubrication for the slidemovement of the pins 26 a and 26 b. In the case where the resinimpregnation is not performed, the grease may be degraded and operationsmay be interfered due to the base oil of the grease taken into theporous portions of the cam 27 through capillarity. However, the resinimpregnation is performed in advance, suppressing the intake of the baseoil and enabling the degradation of the grease to be prevented.

Note that additional processing such as polishing for increasing thesmoothness may be performed on the grooves 27 a and 27 b and thecircular hole 27 c of the cam 27.

Assembly of Grasping Device 10

FIG. 10 is a flowchart illustrating an assembling step for the graspingdevice 10, and FIG. 11 is a perspective view illustrating a state ineach assembling step for the grasping device 10. In FIG. 10 and FIG. 11, first, the driving part 30 including the motor 31 is prepared (stepS21). Next, the driving part 30 and the fixing part 40 are fixed (stepS22). At this time, the opening 44 of the fixing part 40 and the annularprotrusion part 38 of the motor 31 define the mutual position. Note thatexamples of the fixing of the driving part 30 and the fixing part 40 atthe fixing part 40 include a method of screw fixing the through holeprovided in the fixing part 40 and the screw hole provided in the motorcase 33 of the motor 31.

Next, the cam 27 is press-fitted to the shaft 32 of the motor 31 of thedriving part 30 (step S23). FIG. 12 is a longitudinal sectional viewillustrating a state of fixing the cam 27 to the shaft 32 of the motor31 of the driving part 30, with the driving part 30 and the likedisposed upside down with respect to FIG. 11 (with the cam 27 located onthe lower side).

In FIG. 12 , the shaft 32 of the motor 31 is rotatably supported bybearings 34 and 35. In addition, a rotor 36 is fixed to the shaft 32,and a stator 37 is fixed at a position at the motor case 33 sideopposite to the outer peripheral surface of the rotor 36 in the axialdirection.

On the other hand, a circular recess part 91 a is provided at a flatmounting base 91 of the press-fitting jig, and, before fixing the cam 27and the shaft 32 of the motor 31, the center of the cam 27 is alignedwith the recess 91 a of the mounting base 91, and the surface of the cam27 where the grooves 27 a and 27 b are formed is placed in contact withthe mounting base 91.

In this state, the driving part 30 and the fixing part 40 are moved overthe cam 27, and the shaft 32 of the motor 31 is aligned over thecircular hole 27 c of the cam 27. Then, the pressing rod 92 of thepress-fitting jig is inserted from the bottom portion side (in thedrawing, the upper side) of the driving part 30 through the hole 42 b ofthe fixing part 40 and hole 33 a of the motor case 33, the end portionof the pressing rod 92 of the press-fitting jig makes contact with theend portion of the shaft 32 at the side opposite to the side fixed tothe cam 27, a force is applied to the pressing rod 92 from the upperside in the drawing, and thus the shaft 32 is press-fitted into thecircular hole 27 c of the cam 27. A protruding part 32 a of the shaft 32protruded from the cam 27 is housed in the recess part 91 a of themounting base 91.

The shaft 32 of the motor 31 and the cam 27 are fixed throughpress-fitting and therefore are tightly fixed by solid to solid contact,and thus a defect of idling due to a bonding strength not strong enoughto withstand a large load is almost eliminated unlike the fixing withadhesion. With the shaft 32 of the motor 31 and the cam 27 reliablyfixed, the reliability in the grasping operation can be improved.

In addition, the fixing with adhesion does not require wiping off theadhesive agent leaked from the bonded portion, while the press-fittingfixing does not require such an operation, simplifying the operation.Further, when the shaft 32 is press-fitted to the cam 27, the forceapplied to the shaft 32 from the pressing rod 92 is directly received bythe mounting base 91. Thus, inappropriate load is not applied to themotor 31, and the motor 31 is not damaged.

Returning to FIG. 10 and FIG. 11 , separately from the driving part 30side, the rails 23 a and 23 b, the slide movement parts 25 a and 25 b,the pins 26 a and 26 b (not visible in FIG. 11 ), and the claw holdingparts 22 a and 22 b are assembled to the rail holding part 24 (stepS24).

Next, the fixing part 40 and the driving part 30 where the cam 27 ispress-fitted to the shaft 32 (step S23) and the rail holding part 24where the rails 23 a and 23 b and the like are assembled (step S24)fixes the fixing part 40 and the rail holding part 24 (step S25). Anexample of the fixing of the fixing part 40 and the rail holding part 24includes fixing, with a screw, the through hole provided in the fixingpart 40 and the screw hole provided in the rail holding part 24.

FIG. 13 is a longitudinal sectional view when the grasping part 20 isfixed to the driving part 30 and the fixing part 40 and illustrates withthe driving part 30 and the like disposed upside down with respect toFIG. 11 (with the cam 27 located on the lower side). In FIG. 13 , asupport rod 94 provided with a recess part 94 a at the leading end isperpendicularly provided upright from a flat mounting base 93 of theassembling jig.

In this state, the rail holding part 24 where the rails 23 a and 23 band the like are assembled is placed around the support rod 94 on themounting base 93, with the claw holding parts 22 a and 22 b located onthe mounting base 93 side. Then, the end of the support rod 94 isinserted with the outer peripheral surface of the leading end of thesupport rod 94 in contact with the inner peripheral surface of acircular hole 24 e provided in the rail holding part 24. At this time,the circular hole 24 e and the support rod 94 make contact with eachother with a slight clearance (gap) that allows for detachment. Theclearance at this time is 10 μm, for example.

FIG. 14 and FIG. 15 are perspective views of the rail holding part 24,FIG. 14 illustrates a state as viewed from the grasping part 20 side (aviewpoint close to FIG. 5 ), FIG. 15 illustrates a state as viewed fromthe driving part 30 side, and the Y-Y cross section in FIG. 15corresponds to the portion of the rail holding part 24 of FIG. 13 .

In FIG. 14 and FIG. 15 , in the rail holding part 24, two wall parts 24b for fixing the rails 23 a and 23 b (FIG. 5 and the like) are formed atone surface of the base part 24 a having a flat plate shape. A circularrecess part 24 c is provided at the rear surface of the base part 24 a.Between the two wall parts 24 b of the base part 24 a, the circular hole24 e is provided at the center and two long holes 24 d are provided tosandwich the circular hole 24 e. The support rod 94 of the assemblingjig is inserted to the circular hole 24 e, as described above. Two longholes 24 d provide a space where the two pins 26 a and 26 b slide.

Returning to FIG. 13 , the circular hole 24 e of the rail holding part24 is inserted to the support rod 94 of the assembling jig, positioning,on the mounting base 93, the center of the rail holding part 24 wherethe rails 23 a and 23 b and the like are assembled. That is, thevertical direction is positioned by the leading ends (in the drawing,the lower ends) of the claw holding parts 22 a and 22 b making contactwith the mounting base 93 and is positioned, in the plane of themounting base 93, by the contact between the outer peripheral surface ofthe support rod 94 and the inner peripheral surface of the circular hole24 e of the rail holding part 24.

In this state, the fixing part 40 and the driving part 30 with the cam27 press-fitted to the shaft 32 have the cam 27 side as the support rod94 side, and the protruding part 32 a at the leading end of the shaft 32is engaged with the recess part 94 a at the end of the support rod 94.The claw holding parts 22 a and 22 b coupled with the pins 26 a and 26 bare fixed to the slide movement parts 25 a and 25 b (FIG. 5 ),respectively, the slide movement parts 25 a and 25 b respectively meshwith the rails 23 a and 23 b (FIG. 5 ), and the rails 23 a and 23 b arefixed to the rail holding part 24. On the other hand, the cam 27 isfixed to the shaft 32 of the motor 31, and the positional relationship(coaxiality) between the rail holding part 24 and the shaft 32 isimportant for the positional relationship between the cam 27 and thepins 26 a and 26 b. In view of this, when the rail holding part 24 sideand the driving part 30 side is assembled, the simple and accuratepositioning can be performed by positioning the rail holding part 24 andthe shaft 32 with reference to the common aligning assembling jig (themounting base 93 and the support rod 94) and fixing the rail holdingpart 24 and the fixing part 40.

Embodiments of the present invention have been described above, but thepresent invention is not limited to the embodiments described above, andvarious modifications are possible without departing from the spirit ofthe present invention.

For example, while the two claw parts slide in the above-describedembodiment, only one of the claw parts may slide to grasp workpiecestogether with the non-slidable claw part.

As described above, a grasping device according to the embodimentincludes claw holding parts supported by rails in a slidable manner, acam including grooves or curved holes having a spiral shape providedaround a rotation center and a hole provided at the rotation center,pins each having one end engaged with the claw holding parts side andthe other end engaged with the groove or the curved hole of the cam, amotor including a shaft to be fixed to the hole of the cam, and a railholding part configured to hold the rails and engage a positioning jigwith an end portion of the shaft at a side fixed to the cam andincluding a hole part with an inner peripheral surface where an outerperipheral surface of the jig is contactable. In this manner, a graspingdevice capable of performing proper contact between the groove of thecam and the pin through accurate positioning and preventing decrease inefficiency of the slide movement and wear of the cam.

In addition, the protruding part configured to engage with the recesspart of the jig is provided at the leading end of the shaft exposed fromthe hole of the cam. This enables the positioning of the shaft to bereliably performed.

In addition, the fixing part for holding the motor is fixed with therail holding part. This enables fixing with the rail holding part to beperformed with the motor fixed with the fixing part.

Moreover, the present invention is not limited to the embodimentdescribed above. A configuration obtained by appropriately combining theabove-mentioned constituent elements is also included in the presentinvention. Further effects and modification examples can be easilyderived by a person skilled in the art. Thus, a wide range of aspects ofthe present invention is not limited to the embodiment described aboveand may be modified variously.

REFERENCE SIGNS LIST

-   10 Grasping device-   20 Grasping part-   22 a, 22 b Claw holding part-   23 a, 23 b Rail-   24 Rail holding part-   27 Cam-   27 a, 27 b Groove-   30 Driving part-   31 Motor-   32 Shaft-   32 a Protruding part-   33 Motor case-   40 Fixing part-   93 Mounting base-   94 Support rod-   94 a Recess part

1. A grasping device, comprising: claw holding parts supported by railsin a slidable manner; a cam including grooves or curved holes having aspiral shape provided around a rotation center and a hole provided atthe rotation center; pins each having one end engaged with the clawholding parts side and the other end engaged with the grooves or thecurved holes of the cam; a motor including a shaft to be fixed to thehole of the cam; and a rail holding part configured to hold the railsand engage a positioning jig with an end portion of the shaft at a sidefixed to the cam and including a hole part with an inner peripheralsurface where an outer peripheral surface of the jig is contactable. 2.The grasping device according to claim 1, wherein a protruding partconfigured to engage with a recess part of the jig is provided at aleading end of the shaft exposed from the hole of the cam.
 3. Thegrasping device according to claim 1, wherein a fixing part configuredto hold the motor is fixed with the rail holding part.
 1. A graspingdevice, comprising: claw holding parts supported by rails in a slidablemanner; a cam including grooves or curved holes having a spiral shapeprovided around a rotation center and a hole provided at the rotationcenter; pins each having one end engaged with the claw holding partsside and the other end engaged with the grooves or the curved holes ofthe cam; a motor including a shaft to be fixed to the hole of the cam;and a rail holding part configured to hold the rails and engage apositioning jig with an end portion of the shaft at a side fixed to thecam and including a hole part with an inner peripheral surface where anouter peripheral surface of the jig is contactable.
 2. The graspingdevice according to claim 1, wherein a protruding part configured toengage with a recess part of the jig is provided at a leading end of theshaft exposed from the hole of the cam.
 3. The grasping device accordingto claim 1 or 2, wherein a fixing part configured to hold the motor isfixed with the rail holding part.